ps, you may refer to page 3-18 and 3-19 of the Intel 8080/8085 assembly language programming manual. If you donot have, I can send you a copy of it in pdf format.
Regards, Felix 2010/5/28 Fung Felix <[email protected]> > Thank you for your explaination on the behavior of DAA. Please note that in > BCD addition, > 74 + 88 = 162. That means after addition and DAA, the accumulator should > hold 62 and carry flag should be 1 and that is the correct behavior. > Otherwise, 100 is missed and you can never make a correct multi-byte BCD > Addition. > > Besides, as I reported seperately, 99+1 after DAA, the accumulator holds A0 > and carry flag > is 0 which is also wrong. > > Based on the above observation, I believe that there must be a bug exist > when doing DAA > conversion. > > Perhaps you should run the hardware and also theck the CPU manual for the > real behavior > of the CPU > Regards, Felix > > > > 2010/5/26 Onkar Shinde <[email protected]> > > Here is the description of DAA instruction I found in - >> http://www.cs.otago.ac.nz/cosc243/lectures/is_detail.pdf >> **************** >> The contents of the accumulator are changed from a binary value to two >> 4-bit binary coded decimal (BCD) digits. This is the only instruction that >> uses the auxiliary flag to perform the binary to BCD conversion, and the >> conversion procedure is described below. S, Z, AC, P, CY flags are altered >> to reflect the results of the operation. >> If the value of the low-order 4-bits in the accumulator is greater than 9 >> or if AC flag is set, the instruction adds 6 to the low-order four bits. >> If the value of the high-order 4-bits in the accumulator is greater than 9 >> or if the Carry flag is set, the instruction adds 6 to the high-order four >> bits. >> **************** >> >> If you run the program in bug description in debug mode, you will find >> that instruction 'adi 088h' is setting both C and AC flags. Hence when >> DAA is executed 6 is added to both high-order and low-order bits and >> both flags are altered, making then 0. >> >> So as per my understanding the behavior is correct here. >> >> -- >> 78+88 in BCD addition missed carry >> https://bugs.launchpad.net/bugs/584093 >> You received this bug notification because you are a direct subscriber >> of the bug. >> >> Status in gnusim8085: Triaged >> >> Bug description: >> With the following program, the carry flag is missed: >> >> mvi a,078h >> adi 088h >> daa >> hlt >> >> please check >> >> regards, Felix Fung >> >> To unsubscribe from this bug, go to: >> https://bugs.launchpad.net/gnusim8085/+bug/584093/+subscribe >> > > -- 78+88 in BCD addition missed carry https://bugs.launchpad.net/bugs/584093 You received this bug notification because you are a member of GNUSim8085 developers, which is subscribed to gnusim8085. Status in gnusim8085: Triaged Bug description: With the following program, the carry flag is missed: mvi a,078h adi 088h daa hlt please check regards, Felix Fung _______________________________________________ Mailing list: https://launchpad.net/~gnusim8085-devel Post to : [email protected] Unsubscribe : https://launchpad.net/~gnusim8085-devel More help : https://help.launchpad.net/ListHelp
